permit returning from files

this allows skipping an entire feature file if a condition is not
fulfilled, without putting the whole body inside a conditional.

Change-Id: I84fe9c94dda58c794fb52c3f163b40563b0db30a
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
(cherry picked from qtbase/525eb337670f61078383c20ad9be274dcf2d0928)